1. Field of the Invention
This invention relates to apparatus for applying a layer of photographic processing liquid to a length of flexible sheet material.
2. Description of The Prior Art
Apparatus for applying a layer of photographic processing liquid to a length of flexible sheet material are generally well known, especially in that field of photography which comprises instant or self-developing type film. It is also well known that some of these processing liquids are subject to the adverse affects of oxidation, as evidenced by U.S. Pat. Nos. 3,307,468 and 2,520,641. The system in the latter patent utilizes nitrogen gas to prevent the oxidation of the processing liquid contained in a tank which is supported at a location remote from the point of application of the processing liquid. At the point of application, the processing liquid is dispensed by a nozzle into a nip between two moving strips of sheet material. The attempt here is to use the two sheets in conjunction with the nozzle to prevent the processing liquid from coming into contact with the ambient atmosphere, an ambitious task to say the least. In any event, the system appears to be cumbersome and expensive and does not take into consideration the purging of the system to remove any foreign matter which may accumulate at the nozzle. In the former patent, i.e., the '468 patent, the ambient air is removed from a reservoir containing the processing liquid and an applicator roller by completely submersing the roller in the liquid thus raising its level to the top of the reservoir. During such movement of the applicator roller, a cover is moved into sealing relation with the top of the reservoir. Again, no provision is made for removing foreign matter from the surface of the processing liquid, which foreign matter may be transferred to the sheet material by the applicator roller thus possibly adversely affecting the processing of any photographic material.